Data concerning the following areas of metabolism will be obtained, in order to further expand and sophisticate our kinetic model of differentiation in Dictyostelium. (1) Krebs cycle. Data are available on the rate of protein turnover and net degradation, and on the rate in vivo of glutamate oxidation. The cellular concentrations of many relevant metabolites are also available. The concentration of acetyl CoA, and the C4 and C6 acids will be determined using thin layer chromatography; the rate of citrate synthesis in vivo will be based on endogenous precursor specific radioactivities following exposure of cells to (C14) pyruvate; a number of key enzymes (e.g., citrate synthetase) will be characterized in vitro. (2) Glucose metabolism. Available data suggest the existence of a uronic acid pathway. Cells will be exposed to (C14) glucose or galactose and subsequently analyzed for UDP-glucuronic acid. Short-term isotope experiments in vivo will provide flux values and examine the consequences of perturbing the system with exogenous glucose. (3) Trehalose metabolism. Trehalose synthetase has been purified and will be kinetically characterized. Investigations will continue into the basis for its latency and the mechanism of its unmasking during differentiation. Parallel studies will be undertaken for trehalase.